摘要:

In order to describe the hyperfine interaction between electrons and systems of several nuclei (extra-hfs or transferred hfs) there has been used in the literature a simple extension of the expression derived for spherical symmetry around one nucleus. The justification of such a procedure is not obvious. There are several difficulties in its way: in non-spherical symmetry there appear non-hermitian terms in the approximate hamiltonian; and one might expect contributions to the hf interaction on one nucleus originating in the electric field due to another.

ISSN:0026-8976    

DOI:10.1080/00268976700100901

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

More than one interaction potential is usually needed to describe the interaction of two atoms not in1S states. It is shown that the contributions to the mean elastic scattering cross sections from these different potentials do not interfere and that the contribution from each potential is weighted proportional to the statistical weight of the corresponding molecular state. This result is proved for like atoms as well as unlike atoms.

ISSN:0026-8976    

DOI:10.1080/00268976700100911

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The intermolecular potential between an atom and a diatomic molecule is expanded in the spherical harmonicsYlmof the angle between the molecular axis and the interparticle axis. Using a perturbation expansion of the diagonal scattering matrix elements in powers of the coefficient ℋ of theY20term in the potential, it is shown that the total cross section averaged over initial rotational quantum statesmjcontains a contributionO(ℋ2)arising predominantly from inelastic events. This contribution is found to have the same energy dependence as that arising from central forces, but is small and barely detectable even under extreme experimental conditions. It is concluded from a simple model for dispersion forces that for neutral molecules the long range part of the potential measured from the slope of the Massey-Mohr plot contains less than a 1 per cent contribution from an angle dependent term in the potential havingP2symmetry. This conclusion is arrived at whether or not the angular momentum of relative motion is coupled to that of internal motion. An approximate coupling scheme of angular momentum is presented that may be useful in discussing other rotational effects accompanying collision. It is pointed out that inelastic events can dominate total cross sections for ion-molecule scattering.

ISSN:0026-8976    

DOI:10.1080/00268976700100921

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The electron spin resonance spectra of solutions containing two differently coordinated complexes of a transition metal ion show line-broadening if interconversion of the two species occurs at the critical rate. The relaxation matrix formulation is used to discuss the lineshapes for spin ½ systems. The result, for the exchange broadening in the fast exchange limit, is the same as that obtained from the modified Bloch equations, provided that the rotational correlation times are much shorter than the lifetimes of the individual complexes.

ISSN:0026-8976    

DOI:10.1080/00268976700100931

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Changes in atomic orbitals (AO) brought about by changes in molecular wavefunctions are studied by minimizing the energy of carbon in atomic valence states appropriate for ions and excited states of alternant hydrocarbons. It is found that positive-ion and triplet-state 2pπAO's are more contracted than in alternant hydrocarbon ground states. Negative-ion and excited-singlet 2pπAO's are more expanded than in the ground states. These AO changes may be negligible for large molecules but are increasingly important for molecules smaller than naphthalene.

ISSN:0026-8976    

DOI:10.1080/00268976700100941

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The free radical CH3CO2=is identified inγ-irradiated polycrystalline sodium acetate. The observed spectrum is compared with predictions based upon simple Hückel calculations using the hetero atom model of the methyl group.

ISSN:0026-8976    

DOI:10.1080/00268976700100951

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Electron spin resonance studies of VO2+in ammonium chloride single crystals have been reported for the first time. Room temperature studies reveal, that there is a very fast re-adjustment of VO2+molecular ion, in the crystal, giving rise to an isotropic spectrum with spin Hamiltonian constantsg= 1·966 ± 0·001 andA= (103·9 ± 0·9) × 10−4cm−1. At a low temperature corresponding to the ordered cubic phase of the host lattice, an anisotropic spectrum is obtained with spin Hamiltonian constants:

ISSN:0026-8976    

DOI:10.1080/00268976700100961

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A modified Mataga SCF approach is applied to triphenylphosphine. The phenyl rings are simultaneously depressed and then rotated in 5° increments. The results obtained are compared with experimental measurements on triphenylphosphine. An approximate pi inversion barrier of 1·36 kcal/mole is obtained.

ISSN:0026-8976    

DOI:10.1080/00268976700100971

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The nuclear-electron Overhauser effect has been investigated at two magnetic fields for phosphorus III and phosphorus V systems.

ISSN:0026-8976    

DOI:10.1080/00268976700100981

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The collision frequencies of thermal electrons in polar gases are investigated. A quantitative discussion is given of the approximations contained in the conventional theory and it is argued that the ‘exact elastic scattering approximation’ of Mittleman and von Holdt is not a valid description. An error in the comparison of theory and experiment is corrected and it is suggested that the discrepancies can be largely attributed to omitted terms in the assumed interaction potentials. A modified formula is presented for the drift velocity of thermal electrons moving in molecular gases under the influence of a small electric field, which takes account of the internal structure of the molecules.

ISSN:0026-8976    

DOI:10.1080/00268976700100991

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor